Method for Selecting Optimal Radio Access Technology and Communication Apparatuses Utilizing the Same

ABSTRACT

A communication apparatus is provided. A first subscriber identity card camps on a first cell, which is associated with a first radio access technology (RAT) and belongs to a first wireless network, via a radio transceiver module. A second subscriber identity card camps on a second cell, which is associated with a second RAT and belongs to a second wireless network, via the radio transceiver module. A processor constructs a first packet switch connection with the first wireless network via the first subscriber identity card to perform data transfer in the first wireless network, measures a first data transfer throughput of the first wireless network when performing the data transfer via the first subscriber identity card, and determines to perform the data transfer in the second wireless network via the second subscriber identity card when a theoretical data transfer throughput corresponding to the second RAT is higher than the first data transfer throughput.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an intelligent subscriber identity cardselection method, and more particularly to an intelligent subscriberidentity card selection method for automatically determining asubscriber identity card having an optimal radio access technology (RAT)to provide optimal communications services.

2. Description of the Related Art

The term “wireless”, normally refers to an electrical or electronicoperation, which is accomplished without the use of a “hard wired”connection. “Wireless communications”, is the transfer of informationover a distance without the use of electrical conductors or wires. Thedistances involved may be short (a few meters for television remotecontrols) or very long (thousands or even millions of kilometers forradio communications). The best known example of wireless communicationsis the cellular telephone. Cellular telephones use radio waves to enablean operator to make phone calls to another party, from many locationsworld-wide. They can be used anywhere, as long as there is a cellulartelephone site to house equipment that can transmit and receive signals,which are processed to transfer both voice and data to and from thecellular telephones.

There are various well-developed and well-defined cellularcommunications technologies. For example, the Global System for Mobilecommunications (GSM) is a well-defined and commonly adoptedcommunications system, which uses time division multiple access (TDMA)technology, which is a multiplex access scheme for digital radio, tosend voice, data, and signalling data (such as a dialed telephonenumber) between mobile phones and cell sites. Furthermore, the GSM alsouses frequency division multiple access (FDMA) technology. The CDMA2000is a hybrid mobile communications 2.5G/3G (generation) technologystandard that uses code division multiple access (CDMA) technology. TheUMTS (Universal Mobile Telecommunications System) is a 3G mobilecommunications system, which provides an enhanced range of multimediaservices over the 2G GSM system. The Wireless Fidelity (Wi-Fi) is atechnology defined by the 802.11b engineering standard and can be usedfor home networks, mobile phones, and video games, to provide ahigh-frequency wireless local area network.

With the advanced development of wireless communications technologies,it is now possible to provide multiple wireless communications servicesusing different or the same communications technologies in one mobilestation (MS). In order to provide an optimal communications services, anintelligent subscriber identity card selection method requests areprovided.

BRIEF SUMMARY OF THE INVENTION

Communication apparatuses and methods for selecting a subscriberidentity card of a communications apparatus having an optimal radioaccess technology (RAT) are provided. An embodiment of a communicationapparatus comprises a radio transceiver module, a first subscriberidentity card, a second subscriber identity card, a memory device and aprocessor. The first subscriber identity card camps on a first cell,which is associated with a first RAT and belongs to a first wirelessnetwork, via the radio transceiver module. The second subscriberidentity card camps on a second cell, which is associated with a secondRAT and belongs to a second wireless network, via the radio transceivermodule. The memory device stores a plurality of theoretical datatransfer throughputs corresponding to different RATs. The processor iscoupled to the first subscriber identity card, the second subscriberidentity card, the memory device and the radio transceiver module. Theprocessor constructs a first packet switch connection with the firstwireless network via the first subscriber identity card to perform datatransfer in the first wireless network, measures a first data transferthroughput of the first wireless network when performing the datatransfer via the first subscriber identity card, obtains a theoreticaldata transfer throughput corresponding to the second RAT from the memorydevice, and determines to perform the data transfer in the secondwireless network via the second subscriber identity card when thetheoretical data transfer throughput corresponding to the second RAT ishigher than the first data transfer throughput.

Another embodiment of a method for selecting a subscriber identity cardof a communications apparatus having an optimal RAT to perform datatransfer, comprises: obtaining a first theoretical data transferthroughput corresponding to a first RAT and a second theoretical datatransfer throughput corresponding to a second RAT, wherein a firstsubscriber identity card is equipped in the communications apparatus andcamps on a first cell, which is associated with the first RAT andbelongs to a first wireless network, and a second subscriber identitycard is equipped in the communications apparatus and camps on a secondcell, which is associated with the second RAT and belongs to a secondwireless network and a radio transceiver module; constructing a firstpacket switch connection with the first wireless network via the firstsubscriber identity card to perform data transfer when the firsttheoretical data transfer throughput is higher than the secondtheoretical data transfer throughput; and performing the data transferin the first wireless network via the first subscriber identity card.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 shows a communication apparatus according to an embodiment of theinvention;

FIG. 2 shows an exemplary network topology according to an embodiment ofthe invention;

FIG. 3 shows an exemplary radio activity schedule of a radio transceivermodule shared by multiple subscriber identity cards according to anembodiment of the invention;

FIG. 4 a shows exemplary theoretical data transfer throughputs ofdifferent RATs stored in the memory device according to an embodiment ofthe invention;

FIG. 4 b shows exemplary theoretical data transfer throughputs ofdifferent RATs stored in the memory device according to anotherembodiment of the invention;

FIG. 4 c shows exemplary theoretical data transfer throughputs ofdifferent RATs stored in the memory device according to yet anotherembodiment of the invention;

FIG. 4 d shows exemplary theoretical data transfer throughputs ofdifferent RATs stored in the memory device according to still anotherembodiment of the invention;

FIG. 5 shows an exemplary scenario of measured data transfer throughputsaccording to an embodiment of the invention;

FIG. 6 is flow chart of a method for selecting a subscriber identitycard having an optimal RAT to perform data transfer according to anembodiment of the invention;

FIG. 7 shows an exemplary scenario of measured data transfer throughputsaccording to another embodiment of the invention;

FIG. 8 is flow chart of a method for selecting a subscriber identitycard having an optimal RAT to perform data transfer according to anotherembodiment of the invention; and

FIG. 9 is flow chart of a method for selecting a subscriber identitycard having an optimal RAT to perform data transfer according to yetanother embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

FIG. 1 shows a communication apparatus according to an embodiment of theinvention. As shown in FIG. 1, a communication apparatus 100 maycomprise more than one subscriber identity card, such as the subscriberidentity cards 101 and 102, as shown, a baseband module 103, and a radiotransceiver module 104, wherein the baseband module 103 is coupled tothe subscriber identity cards 101 and 102, and the radio transceivermodule 104. The radio transceiver module 104 receives wireless radiofrequency signals, converts the received signals to baseband signals tobe processed by the baseband module 103, or receives baseband signalsfrom the baseband module 103 and converts the received signals towireless radio frequency signals to be transmitted to a peer device. Theradio transceiver module 104 may comprise a plurality of hardwaredevices to perform radio frequency conversion. For example, the radiotransceiver module 104 may comprise a mixer to multiply the basebandsignals with a carrier oscillated in the radio frequency of the wirelesscommunication system, wherein the radio frequency may be, for example,900 MHz or 1800 MHz for a global system for mobile communication (GSM),or 1900 MHz for a Universal Mobile Telecommunications System (UMTS), orothers. The baseband module 103 further converts the baseband signals toa plurality of digital signals, and processes the digital signals, andvice versa. The baseband module 103 may also comprise a plurality ofhardware devices to perform baseband signal processing. The basebandsignal processing may comprise analog to digital conversion(ADC)/digital to analog conversion (DAC), gain adjustment,modulation/demodulation, encoding/decoding, and so on. The basebandmodule 103 further comprises a memory device 106 and a processor 105 forcontrolling the operations of the baseband module 103, the radiotransceiver module 104, and the subscriber identity cards 101 and 102plugged into two sockets, respectively. The processor 105 reads datafrom the plugged subscriber identity cards 101 and 102 and writes datato the plugged subscriber identity cards 101 and 102. Note that thememory device 106 may also be configured outside of the baseband module103 and the invention should not be limited thereto. Note also that FIG.1 only shows one exemplary embodiment of the invention so as to simplifythe description of the invention for a clearer understanding of theconcepts the invention. Any wireless communications module that canprovide wireless communications services may also be integrated withinthe invention and the invention should not be limited thereto. Inaddition, each module as previously described may be implemented as asingle chip for providing corresponding functions, or may be integratedinto a combo chip (i.e., a system on chip (SoC)), and the inventionshould not be limited thereto.

FIG. 2 shows an exemplary network topology according to an embodiment ofthe invention. The communication apparatus 100, equipped with more thanone subscriber identity card, may simultaneously access more than one ofthe wireless networks 203 and 204 of the same or different radio accesstechnologies (RATs), after camping on or associating with the cellsmanaged by the access stations 201 and 202, where the access stations201 or 202 may be a base station, a node-B, or an access pointcompatible with the 802.1a, 802.1b or 802.1g standards, or others. Forexample, the wireless network 203 and/or the wireless network 204 may bethe GSM, WCDMA, Wi-Fi, CDMA2000 or Time Division-Synchronous CodeDivision Multiple Access (TD-SCDMA) network, or Internet, or the like.The communication apparatus 100 may issue an apparatus originatedcommunication request, such as a voice call, a data call, a video call,or a voice over Internet Protocol (VOIP) call, to a called party (i.e.the corresponding peer of another wired or wireless communicationapparatus) through at least one of the networks 203 and 204 withcorresponding intermediary apparatuses 205 and 206 (for example, the GSMnetwork with a Mobile Switching Center (MSC), the WCDMA/TD-SCDMA networkwith a Radio Network Controller (RNC), or the Internet with a SessionInitiation Protocol (SIP) server), or through the Public SwitchedTelephone Network (PSTN) 207 or any combinations thereof, by using anyof the equipped subscriber identity cards. Moreover, the communicationapparatus 100 may receive an apparatus terminated communication request,also referred to as mobile terminated (MT) call request, such as anincoming phone call, with any of the subscriber identity cards from acalling party. It is to be understood that there may be one or moregateways positioned between heterogeneous types of networks.

According to an embodiment of the invention, the subscriber identitycards 101 and 102 may correspond to one type of wireless communicationssystem. For example, the subscriber identity cards 101 or 102 may be thesubscriber identity module (SIM) card corresponding to the GSMcommunications system, or the universal subscriber identity module(USIM) card corresponding to the UMTS communications system, or theremovable user identity module (RUIM) card or the CDMA SubscriberIdentity Module (CSIM) card corresponding to the CDMA2000 communicationsystem, or others.

FIG. 3 shows an exemplary radio activity schedule of a radio transceivermodule shared by multiple subscriber identity cards according to anembodiment of the invention. In the embodiment, the radio transceivermodule 104 is shared by the subscriber identity cards 101 and 102, andis switched to perform packet switch (PS) data transfer of thesubscriber identity card 101 (hereinafter called the first subscriberidentity card) during the time period TP1. However, within the timeperiod TP1, a portion of time is punctured by the subscriber identitycard 102 (hereinafter called the second subscriber identity card) sothat the radio transceiver module 104 is switched to perform the radioactivity of the second subscriber identity card. During the puncturedtime period TP2, the second subscriber identity card may perform anytask that would be performed during an idle mode, such as listening tothe broadcast channel, control channel, or paging indication channel ormeasuring signal qualities of serving or neighboring cells, or others,via the radio transceiver module 104. Note that in the conventionaldesign, the second subscriber identity card may enter a “flight mode” tosuspend its transmitting and receiving functions when the radio resourceis occupied by the first subscriber identity card to perform CS voice orPS data transfer. However, based on the concept of the invention, thesecond subscriber identity card may enter a “virtual idle mode” when theradio transceiver module 104 is mainly occupied by the first subscriberidentity card to perform PS data transfer (thus, the first subscriberidentity card is in a packet transfer mode (PTM)), and does not have tosuspend its transmitting and receiving functions. In the preferredembodiments, two protocol stacks may be implemented so as torespectively handle the radio activities of the first and secondsubscriber identity cards. However, it is also possible to implementonly one protocol stack to handle the radio activities of the first andsecond subscriber identity cards at the same time, and the inventionshould not be limited thereto.

According to an embodiment of the invention, because the secondsubscriber identity card may enter a “virtual idle mode” while the firstsubscriber identity card is performing PS data transfer (i.e. in thepacket transfer mode (PTM)), the second subscriber identity card mayperform an inter-RAT change procedure to camp on an optimal cell (i.e. acell associated with a more advanced RAT) by using the punctured timeperiod. When the second subscriber identity card camps on an optimalcell, which may be judged by the processor 105 to have a higher datatransfer throughput than the current RAT associated with the firstidentity card, the processor 105 may transfer the operation of theongoing PS data transfer from the first subscriber identity card to thesecond subscriber identity card, so as to provide optimal PS datatransfer for the communications apparatus user. This procedure may becalled, inter subscriber identity card reselection.

According to an embodiment of the invention, a plurality of theoreticaldata transfer throughputs corresponding to different RATs may be storedin the memory device 106. FIG. 4 a shows exemplary theoretical datatransfer throughputs of different RATs stored in the memory deviceaccording to an embodiment of the invention. In this embodiment, thetheoretical data transfer throughputs may be the maximum or minimumdownlink throughput defined in the specifications associated withdifferent RATs. For example, the minimum downlink throughput ofdifferent RATs, including the 2G/2.5G, 3G/3.5G and 4G RATs, is shown inFIG. 4 a, where the throughput may be defined as the amount of data thatcan be transmitted per second (i.e. kbps). FIG. 4 b shows exemplarytheoretical data transfer throughputs of different RATs stored in thememory device according to another embodiment of the invention. In thisembodiment, the experimental downlink throughputs of different RATs,which may be an averaged result obtained from several experiments (forexample, Lab experiments, field tries, or others), are taken as thetheoretical data transfer throughputs. FIG. 4 c shows exemplarytheoretical data transfer throughputs of different RATs stored in thememory device according to yet another embodiment of the invention. Inthis embodiment, the observed downlink throughputs of different RATs,which may be an averaged result obtained through previous practicalexperiences, are taken as the theoretical data transfer throughputs.FIG. 4 d shows exemplary theoretical data transfer throughputs ofdifferent RATs stored in the memory device according to still anotherembodiment of the invention. In this embodiment, the expected downlinkthroughputs of different RATs, which may be obtained by taking anaverage of the maximum and minimum downlink throughputs defined bydifferent RAT specifications, are taken as the theoretical data transferthroughputs. Note that the theoretical data transfer throughputscorresponding to different RATs with respect to different subscriberidentity cards may also be respectively stored in the memory device 106.Further, the theoretical data transfer throughputs may also be obtainedby ways other than what is shown in FIGS. 4 a-4 d, and therefore, theinvention should not be limited thereto.

As previously described, because the second subscriber identity card mayenter a “virtual idle mode” when the first subscriber identity card isin the packet transfer mode (PTM), the processor 105 may obtain atheoretical data transfer throughput corresponding to the second RATthat is associated with the second cell camped on by the secondsubscriber identity card from the memory device 106, and determine toperform the data transfer in the second wireless network via the secondsubscriber identity card when the theoretical data transfer throughputcorresponding to the second RAT is higher than a measured data transferthroughput corresponding to the first RAT associated with the first cellcamped on by the first subscriber identity card. Note that themeasurement of the data transfer throughput corresponding to the firstRAT may be performed periodically or may be triggered by predeterminedevents. FIG. 5 shows an exemplary scenario of measured data transferthroughputs according to an embodiment of the invention. In theembodiment, the processor 105 may begin to construct a first packetswitch connection with a first wireless network, which is a 2G network,via the first subscriber identity card to perform the PS data transferin the first wireless network from time t1. When performing the PS datatransfer, the processor 105 may further measure the data transferthroughputs of the first wireless network to obtain data which is shownas a curve of measured data transfer throughputs as shown in FIG. 5. Atthe same time, the second subscriber identity card may enter the virtualidle mode and keep performing its transmitting and receiving schedulesin the punctured time. Suppose that the second subscriber identity cardhas camped on the second cell, which may be a 4G cell, at time t2, theprocessor 105 may obtain a theoretical 4G data transfer throughput fromthe memory device 106, for example, a minimum downlink throughputMinTP_(—)4G defined by the specification as shown, and compare theobtained theoretical 4G data transfer throughput with a first practicaldata transfer throughput corresponding to the ongoing PS data transfer.The first practical data transfer throughput may be obtained by anaveraged result of the measured data transfer throughputs obtained overa period of time, a maximum/minimum value of the obtained measured datatransfer throughputs, or other.

When the theoretical 4G data transfer throughput is higher than thefirst practical data transfer throughput corresponding to the ongoing PSdata transfer, the processor 105 may determine to perform the PS datatransfer in the second wireless network via the second subscriberidentity card. For example, in one embodiment, the processor 105 maysuspend the ongoing PS data transfer in the first wireless network,disconnect the first packet switch connection with the first wirelessnetwork, construct a second packet switch connection with the secondwireless network via the second subscriber identity card, and resume thePS data transfer in the second wireless network. As shown in FIG. 5, theprocessor 105 may suspend the ongoing PS data transfer in the firstwireless network and disconnect the first packet switch connection withthe first wireless network at time t2, and start to construct a secondpacket switch connection with the second wireless network via the secondsubscriber identity card and resume the PS data transfer in the secondwireless network at time t3. The time gap from the time t2 to t3 is thetransition time required due to the switching of the radio transceivermodule 104. Because the 4G network has a theoretical data transferthroughput which is higher than that of the first practical datatransfer throughput of the 2G network, it is highly possible to improvethe data transfer throughput at time t3.

According to an embodiment of the invention, the processor 105 mayobtain a theoretical data transfer throughput of the RAT correspondingto the subscriber identity card in the virtual idle mode and compare thetheoretical data transfer throughput with the first practical datatransfer throughput when the subscriber identity card in the virtualidle mode has camp on a cell. For example, the radio transceiver module104 may be switched to perform a camp on procedure to facilitate thesubscriber identity card in the virtual idle mode to camp on a cell whenthe other subscriber identity card is in the packet transfer mode (PTM).As defined by the TS43.022 (2G) specification, being camped on a cellmeans that the mobile station (MS) has completed a cellselection/reselection process and has chosen a cell from which it plansto receive all available services. For normal services, normal campingmeans that the MS has to camp on a suitable cell, and tune to thatcell's control channel(s). In addition, as defined by the TS 25.304 (3G)specification, being camped on a cell means that the user equipment (UE)has completed the cell selection/reselection process and has chosen acell. The UE monitors system information and (in most cases) paginginformation. In addition, the UE searches for a suitable cell of theselected public land mobile network (PLMN) and chooses that cell toprovide available services, and tunes to its control channel. Thechoosing is known as “camping on a cell”. Note that a person withordinary skill in the art will readily appreciate or deduce that thedefinition of camping on a cell may apply to other developed or to bedeveloped RATs. Thus, the definitions described in the specificationcorresponding to other RATS are omitted here for brevity.

According to another embodiment of the invention, the processor 105 mayalso obtain a theoretical data transfer throughput of the RATcorresponding to the subscriber identity card in the virtual idle modeand compare the theoretical data transfer throughput with the firstpractical data transfer throughput when the subscriber identity card inthe virtual idle mode has changed its RAT. For example, the radiotransceiver module 104 may be switched to perform an inter-RAT changeprocedure to facilitate the subscriber identity card in the virtual idlemode to camp on a cell associated with a different RAT during a periodof performing data transfer via the other subscriber identity card thatis in the packet transfer mode (PTM). The scenarios that can causechanges in RATs may include, but are not limited to, inter-RATselection, inter-RAT reselection, cell change order, or others. Asdefined by the 3GPP 45.008 6.6.5/6.6.6 specification, the MS shall thenreselect a suitable (see the specification 3GPP TS 25.304) UniversalTerrestrial Radio Access Network (UTRAN) cell if: for a Time-divisionduplex (TDD) cell, the measured received signal code power (RSCP) valueis equal to or greater than TDD_Qoffset for a period of 5 s, and, for aFrequency-division duplex (FDD) cell, the following criteria are all metfor a period of 5 seconds, including 1) its measured RSCP value exceedsthe value of RLA_C for the serving cell and all of the suitable (see thespecification 3GPP TS 43.022) non-serving GSM cells by the valueFDD_Qoffset, 2) its measured Ec/No value is equal or greater than thevalue (FDD_Qmin−FDD_Qmin_Offset), and 3) its measured RSCP value isequal to or greater than FDD RSCP threshold.

As defined by the 3GPP 25.304 5.2.2.1 specification, whenever a PLMN hasbeen selected by Non Access Stratum (NAS), the UE shall attempt to finda suitable cell to camp on. The NAS may control the cell selectionby: 1) providing information on RAT(s) associated with the selectedPLMN, 2) maintaining lists of forbidden registration areas; and 3)providing a list of equivalent PLMNs. As defined by the 3GPP 25.3318.3.10.1 specification, the purpose of the inter-RAT cell change orderto UTRAN procedure is to transfer, under the control of the source,radio access technology, a connection between the UE and another radioaccess technology (e.g. GSM/GPRS) to UTRAN. Note that the person ofordinary skill in the art will readily appreciate or deduce thedefinition of camped on a cell in other developed or to be developedRATs, and for the definitions described in the specificationscorresponding to other RATS are omitted here for brevity.

Referring back to FIG. 5, according to an embodiment of the invention,before the first packet switch connection is disconnected, the processor105 may further record the first practical data transfer throughputwhich corresponds to the first RAT measured during the time period fromt1 to t2, and store the recorded first practical data transferthroughput in the memory device 106 as an expected data transferthroughput. After the processor 105 determines to perform PS datatransfer in the second wireless network via the second subscriberidentity card, the processor 105 may also measure and monitor athroughput of the second wireless network during a period of performingthe data transfer via the second subscriber identity card over apredetermined time period, so as to obtain a second practical datatransfer throughput and compare the second practical data transferthroughput with the expected data transfer throughput. Note that themeasurement of the data transfer throughput corresponding to the secondwireless network may be performed periodically or may be triggered bypredetermined events. When the expected data transfer throughput ishigher than the second data transfer throughput, the processor 105 maydetermine to transfer the data transfer procedure back to the firstsubscriber identity card.

FIG. 6 is flow chart of a method for selecting a subscriber identitycard having an optimal RAT to perform data transfer according to anembodiment of the invention. When performing PS data transfer via afirst subscriber identity card (Step S601), the processor 105 may checkwhether one of the criteria for an inter subscriber identity cardreselection has been met (Step S602). According to the embodiments ofthe invention, the criteria may be, for example, a second subscriberidentity card in the virtual idle mode is camped on a cell associatedwith a RAT that is more advanced than the RAT currently being used fortransferring the PS data, or a second subscriber identity card in thevirtual idle mode has changed its RAT to a more advanced one than theone currently being used for transferring the PS data, or a secondsubscriber identity card in the virtual idle mode can support a RAT thatis more advanced than the one currently being used for transferring thePS data, or others. Note that in the embodiments, the term “moreadvanced” means a higher supported data transfer throughput. When one ofthe criteria for the inter subscriber identity card reselection has met,the processor 105 may suspend the current PS data transfer process anddisconnect the current PS connection (Step S603). Next, the processor105 may activate the second subscriber identity card, which is in thevirtual idle mode and has met the inter subscriber identity cardreselection criteria, and then start the access procedure of the secondsubscriber identity card, construct a PS connection with the wirelessnetwork and resume the PS data transfer via the second subscriberidentity card (Step S604).

After the PS data transfer process is performed via the secondsubscriber identity card, the processor 105 may further check whetherthe current data transfer throughput is lower than an expected datatransfer throughput (Step S605). As previously described, the processor105 may record the data transfer throughput measured before the PSconnection of the first subscriber identity card is disconnected as theexpected data transfer throughput. When the current data transferthroughput is lower than the expected data transfer throughput, theprocessor 105 may determine to transfer the PS data transfer processback to the first subscriber identity card. Similarly, the processor 105may suspend the current PS data transfer process and disconnect thecurrent PS connection (Step S606), and further activate the firstsubscriber identity card, and then start the access procedure of thefirst subscriber identity card, construct a PS connection with thewireless network and resume the PS data transfer via the firstsubscriber identity card (Step S607).

FIG. 7 shows an exemplary scenario of measured data transfer throughputsaccording to another embodiment of the invention. The scenario beginningfrom time t1 to t3 as shown in FIG. 7 is the same as the scenario shownin FIG. 5. In other words, during the time period from time t1 to t2,the PS data transfer process is performed on the first subscriberidentity card, and after the time t3, the PS data transfer process isperformed on the second subscriber identity card. However, from time t4,the data transfer throughput dramatically drops, and the processor 105determines that the current data transfer throughput is lower than theexpected data transfer throughput Expected_TP. Because the current datatransfer throughput is lower than the expected data transfer throughputExpected_TP, the processor 105 may determine to transfer the PS datatransfer process back to the first subscriber identity card at time t5.Therefore, from the time t6, the PS data transfer process is performedon the first subscriber identity card.

According to another embodiment of the invention, when the current datatransfer throughput is lower than the expected data transfer throughput,the processor 105 may further record an identifier corresponding to thecell having the current data transfer throughput lower than the expecteddata transfer throughput in a black list. According to an embodiment ofthe invention, the identifier corresponding to the cell may be the cellidentity of that cell. The black list may be stored in the memory device106 as another criteria to determine whether the inter subscriberidentity card reselection should be performed. For example, the intersubscriber identity card reselection should be performed when thesubscriber identity card in the virtual idle mode is camped on a cellassociated with a RAT that is more advanced than the RAT currently beingused for transferring the PS data, and the cell associated with the moreadvanced RAT is not in the black list. For another example, the intersubscriber identity card reselection should be performed when thesubscriber identity card in the virtual idle mode has changed its RAT toa more advanced one than the one currently being used for transferringthe PS data, and the cell associated with the more advanced RAT is notin the black list. For yet another example, the inter subscriberidentity card reselection should be performed when the subscriberidentity card in the virtual idle mode can support a RAT that is moreadvanced than the one currently being used for transferring the PS data,and the cell associated with the more advanced RAT is not in the blacklist.

FIG. 8 is flow chart of a method for selecting a subscriber identitycard having an optimal RAT to perform data transfer according to anembodiment of the invention. In this embodiment, when performing PS datatransfer via a first subscriber identity card (Step S801), the processor105 may check whether one of the criteria for an inter subscriberidentity card reselection has been met (Step S802). As previouslydescribed, the criteria may be, for example, a second subscriberidentity card in the virtual idle mode has camped on a cell associatedwith a RAT that is more advanced than the RAT currently being used fortransferring the PS data, or a second subscriber identity card in thevirtual idle mode has changed its RAT to a more advanced one than theone currently being used for transferring the PS data, or a secondsubscriber identity card in the virtual idle mode can support a RAT thatis more advanced than the one currently being used for transferring thePS data, or others. When the criteria for the inter subscriber identitycard reselection has been met, the processor 105 may further determinewhether an identity of the cell camped on by the second subscriberidentity card is not stored in the black list (Step S803). When theidentity of the cell camped on by the second subscriber identity card isnot stored in the black list, the processor 105 may begin the intersubscriber identity card reselection process to suspend the current PSdata transfer process and disconnect the current PS connection (StepS804). Next, the processor 105 may activate the second subscriberidentity card, which is in the virtual idle mode and has met the intersubscriber identity card reselection criteria, and then start the accessprocedure of the second subscriber identity card, construct a PSconnection with the wireless network and resume the PS data transfer viathe second subscriber identity card (Step S805).

After the PS data transfer process is performed via the secondsubscriber identity card, the processor 105 may further check whetherthe current data transfer throughput is lower than an expected datatransfer throughput (Step S806). As previously described, the processor105 may record the data transfer throughput measured beforedisconnecting the current PS connection of the first subscriber identitycard as the expected data transfer throughput. When the current datatransfer throughput is lower than the expected data transfer throughput,the processor 105 may determine to transfer the PS data transfer processback to the first subscriber identity card. Similarly, the processor 105may suspend the current PS data transfer process and disconnect thecurrent PS connection (Step S807), and further activate the firstsubscriber identity card, and then start the access procedure of thefirst subscriber identity card, construct a PS connection with thewireless network and resume the PS data transfer via the firstsubscriber identity card (Step S808). In addition, the processor 105 mayfurther record the identifier corresponding to the cell camped on by thesecond subscriber identity card in the black list for future use (StepS809). Note that in some embodiments of the invention, the recordedidentifier may be removed from the black list after a predetermined timeperiod.

According to another embodiment of the invention, the concept ofselecting a subscriber identity card having an optimal RAT may also beapplied when constructing a PS connection. For example, according to anembodiment of the invention, for the dual subscriber identity cardexample as shown in FIG. 1, the processor 105 may obtain a firsttheoretical data transfer throughput corresponding to a first RATassociated with a first cell camped on by a first subscriber identitycard and a second theoretical data transfer throughput corresponding toa second RAT associated with a second cell camped on by a secondsubscriber identity card from the memory device 106, and begin toconstruct the PS connection with the wireless network via the subscriberidentity card having the higher theoretical data transfer throughput. Inaddition, when the first theoretical data transfer throughput is thesame as the second theoretical data transfer throughput, the processor105 may further obtain a third theoretical data transfer throughputcorresponding to the most advanced RAT supported by the first subscriberidentity card and a fourth theoretical data transfer throughputcorresponding to the most advanced RAT supported by the secondsubscriber identity card, and begin to construct the PS connection withthe wireless network via the subscriber identity card having the highertheoretical data transfer throughput.

For example, supposed that the RATs supported by the first subscriberidentity card are 2G and 3G RATs, and the RATs supported by the secondsubscriber identity card are 2G, 3G and 4G RATs. When the firstsubscriber identity card has camped on a 3G cell and the secondsubscriber identity card has camped on a 2G cell, the theoretical datatransfer throughput corresponding to the 3G cell is generally higherthan that of the 2G cell. Therefore, the processor 105 may select toperform PS data transfer via the first subscriber identity card. Foranother example, when both the first subscriber identity card and thesecond subscriber identity card have camped on 2G cells, the theoreticaldata transfer throughputs corresponding to the 2G cells may be the same.Therefore, the processor 105 may select to perform PS data transfer viathe second subscriber identity card because the most advanced RATsupported by the second subscriber identity card is 4G, which issupposed to have a higher theoretical data transfer throughput than the3G RAT (the most advanced RAT supported by the first subscriber identitycard). Note that in some embodiments of the invention, since differentRATs may use different transmission bands, the RAT associated with thecurrently camped on cell may be obtained according to the frequency ofthe transmission bands. Note also that in other embodiments of theinvention, information regarding the most advanced RAT that can besupported by the subscriber identity card may be obtained from thecorresponding subscriber identity card (such as the related ElementaryFile (EF) stored in the SIM, the USIM, the RUIM, or the likes), orobtained according to hardware or software configurations of thecommunications apparatus, or obtained from the operators of the wirelessnetworks, or any combinations thereof

FIG. 9 is flow chart of a method for selecting a subscriber identitycard having an optimal RAT to perform data transfer according to yetanother embodiment of the invention. After receiving an instruction tobegin PS data transfer (Step S901), the processor 105 may firstdetermine whether an optimal RAT can be found from the current RATsassociated with the cells currently camped on by different subscriberidentity cards (Step S902). When an optimal RAT can be found from thecurrent RATs, for example, a current RAT having a higher theoreticaldata transfer throughput than other RATs can be found, the processor 105may use the subscriber identity card camping on a cell associated withthe optimal RAT as a preferred subscriber identity card, and perform thePS data transfer via the subscriber identity card (Step S903). When anoptimal RAT can not be found from the current RATs, for example, whenthe current RATs associated with the cells currently camped on bydifferent subscriber identity cards are the same or have the sametheoretical data transfer throughputs, the processor 105 may furtherdetermine whether an optimal RAT can be found from the supported RATscorresponding to different subscriber identity cards (Step S904). Whenan optimal RAT can be found from supported RATs, for example, when themost advanced RAT that can be supported by a subscriber identity cardhas a higher theoretical data transfer throughput than other RATs, theprocessor 105 may use the subscriber identity card camping on a cellassociated with the optimal supported RAT as a preferred subscriberidentity card, and perform the PS data transfer via the subscriberidentity card (Step S905). On the other hand, when an optimal supportedRAT can not be found, the processor 105 may randomly select a subscriberidentity card, or use a user defined subscriber identity card, andperform the PS data transfer via the subscriber identity card (StepS906).

The above-described embodiments of the present invention can beimplemented in any of numerous ways. For example, the embodiments may beimplemented using hardware, software or a combination thereof. It shouldbe appreciated that any component or collection of components thatperform the functions described above can be generically considered asone or more processors that control the above discussed function. Theone or more processors can be implemented in numerous ways, such as withdedicated hardware, or with general purpose hardware that is programmedusing microcode or software to perform the functions recited above.

Use of ordinal terms such as “first”, “second”, “third”, etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

While the invention has been described by way of example and in terms ofpreferred embodiment, it is to be understood that the invention is notlimited thereto. Those who are skilled in this technology can still makevarious alterations and modifications without departing from the scopeand spirit of this invention. Therefore, the scope of the presentinvention shall be defined and protected by the following claims andtheir equivalents.

1. A communications apparatus, comprising: a processor, coupled to afirst subscriber identity card, a second subscriber identity card, amemory device and a radio transceiver module, wherein the firstsubscriber identity card camps on a first cell, which is associated witha first radio access technology (RAT) and belongs to a first wirelessnetwork, via the radio transceiver module; wherein the second subscriberidentity card camps on a second cell, which is associated with a secondRAT and belongs to a second wireless network, via the radio transceivermodule; wherein the memory device stores a plurality of theoretical datatransfer throughputs corresponding to different RATs; and wherein theprocessor constructs a first packet switch connection with the firstwireless network via the first subscriber identity card to perform datatransfer in the first wireless network, measures a first data transferthroughput of the first wireless network when performing the datatransfer via the first subscriber identity card, obtains a theoreticaldata transfer throughput corresponding to the second RAT from the memorydevice, and determines to perform the data transfer in the secondwireless network via the second subscriber identity card when thetheoretical data transfer throughput corresponding to the second RAT ishigher than the first data transfer throughput.
 2. The communicationapparatus as claimed in claim 1, wherein the processor further suspendsthe data transfer in the first wireless network, disconnects the firstpacket switch connection with the first wireless network, constructs asecond packet switch connection with the second wireless network via thesecond subscriber identity card, and resumes the data transfer in thesecond wireless network.
 3. The communication apparatus as claimed inclaim 1, wherein the radio transceiver module is switched to perform acamp on procedure of the second subscriber identity card to facilitatethe second subscriber identity card to camp on the second cell during aperiod of performing the data transfer via the first subscriber identitycard.
 4. The communication apparatus as claimed in claim 1, wherein theradio transceiver module is switched to perform an inter-RAT changeprocedure of the second subscriber identity card to facilitate thesecond subscriber identity card to camp on the second cell during aperiod of performing the data transfer via the first subscriber identitycard.
 5. The communication apparatus as claimed in claim 2, wherein theprocessor further records the first data transfer throughput measuredbefore the first packet switch connection is disconnected in the memorydevice.
 6. The communication apparatus as claimed in claim 5, whereinthe processor further measures and monitors a throughput of the secondwireless network when performing the data transfer via the secondsubscriber identity card over a predetermined time period to obtain asecond data transfer throughput, and compares the second data transferthroughput with the recorded first data transfer throughput, anddetermines to perform the data transfer in the first wireless networkvia the first subscriber identity card when the recorded first datatransfer throughput is higher than the second data transfer throughput.7. The communication apparatus as claimed in claim 6, wherein theprocessor further suspends the data transfer in the second wirelessnetwork, disconnects the second packet switch connection with the secondwireless network, constructs a third packet switch connection with thefirst wireless network via the first subscriber identity card, andresumes the data transfer in the first wireless network.
 8. Thecommunication apparatus as claimed in claim 6, wherein the processorfurther records an identifier corresponding to the second cell in ablack list when the recorded first data transfer throughput is higherthan the second data transfer throughput.
 9. The communication apparatusas claimed in claim 1, wherein the processor further checks whether anidentifier corresponding to the second cell is in a black list anddetermines to perform the data transfer in the second wireless networkvia the second subscriber identity card when the identifiercorresponding to the second cell is not in the black list.
 10. Thecommunication apparatus as claimed in claim 1, wherein before performingthe data transfer, the processor further obtains a first theoreticaldata transfer throughput corresponding to the first RAT and a secondtheoretical data transfer throughput corresponding to the second RATfrom the memory device, and begins to construct the first packet switchconnection with the first wireless network via the first subscriberidentity card to perform the data transfer in the first wireless networkwhen the first theoretical data transfer throughput is higher than thesecond theoretical data transfer throughput.
 11. The communicationapparatus as claimed in claim 1, wherein before performing the datatransfer, the processor further obtains a first theoretical datatransfer throughput corresponding to a most advanced RAT supported bythe first subscriber identity card and a second theoretical datatransfer throughput corresponding to a most advanced RAT supported bythe second subscriber identity card from the memory device, and beginsto construct the first packet switch connection with the first wirelessnetwork via the first subscriber identity card to perform the datatransfer in the first wireless network when the first theoretical datatransfer throughput is higher than the second theoretical data transferthroughput.
 12. A method for selecting a subscriber identity card of acommunications apparatus having an optimal radio access technology (RAT)to perform data transfer, comprising: obtaining a first theoretical datatransfer throughput corresponding to a first RAT and a secondtheoretical data transfer throughput corresponding to a second RAT,wherein a first subscriber identity card is equipped in thecommunications apparatus and camps on a first cell, which is associatedwith the first RAT and belongs to a first wireless network, and a secondsubscriber identity card is equipped in the communications apparatus andcamps on a second cell, which is associated with the second RAT andbelongs to a second wireless network and a radio transceiver module;constructing a first packet switch connection with the first wirelessnetwork via the first subscriber identity card to perform data transferwhen the first theoretical data transfer throughput is higher than thesecond theoretical data transfer throughput; and performing the datatransfer in the first wireless network via the first subscriber identitycard.
 13. The method as claimed in claim 12, further comprising:obtaining a third theoretical data transfer throughput corresponding toa most advanced RAT supported by the first subscriber identity card anda fourth theoretical data transfer throughput corresponding to a mostadvanced RAT supported by the second subscriber identity card when thefirst RAT is the same as the second RAT; constructing the first packetswitch connection with the first wireless network via the firstsubscriber identity card when the third theoretical data transferthroughput is higher than the fourth theoretical data transferthroughput; and performing the data transfer in the first wirelessnetwork via the first subscriber identity card.
 14. The method asclaimed in claim 12, further comprising: measuring a first practicaldata transfer throughput of the first wireless network when performingthe data transfer via the first subscriber identity card; comparing thefirst practical data transfer throughput with the second theoreticaldata transfer throughput; and performing the data transfer in the secondwireless network via the second subscriber identity card when the secondtheoretical data transfer throughput is higher than the first practicaldata transfer throughput.
 15. The method as claimed in claim 14, furthercomprising: suspending the data transfer in the first wireless network;disconnecting the first packet switch connection with the first wirelessnetwork; constructing a second packet switch connection with the secondwireless network via the second subscriber identity card; and resumingthe data transfer in the second wireless network.
 16. The method asclaimed in claim 14, further comprising: suspending the data transfer inthe first wireless network when performing the data transfer via thefirst subscriber identity card; switching the radio transceiver moduleto perform a camp on procedure of the second subscriber identity card tofacilitate the second subscriber identity card to camp on a third cellassociated with a third RAT; and obtaining a fifth theoretical datatransfer throughput corresponding to the third RAT and comparing thefirst practical data transfer throughput with the fifth theoretical datatransfer throughput after the second subscriber identity card has campedon the third cell.
 17. The method as claimed in claim 14, furthercomprising: suspending the data transfer in the first wireless networkwhen performing the data transfer via the first subscriber identitycard; switching the radio transceiver module to perform an inter-RATchange procedure of the second subscriber identity card to facilitatethe second subscriber identity card to camp on a third cell associatedwith a third RAT; and obtaining a fifth theoretical data transferthroughput corresponding to the third RAT and comparing the firstpractical data transfer throughput with the fifth theoretical datatransfer throughput after the second subscriber identity card has campedon the third cell.
 18. The method as claimed in claim 15, furthercomprising: recording the first practical data transfer throughputmeasured before the first packet switch connection is disconnected in amemory device.
 19. The method as claimed in claim 18, furthercomprising: measuring and monitoring a throughput of the second wirelessnetwork when performing the data transfer via the second subscriberidentity card over a predetermined time period to obtain a secondpractical data transfer throughput; comparing the second practical datatransfer throughput with the recorded first practical data transferthroughput; and performing the data transfer in the first wirelessnetwork via the first subscriber identity card when the recorded firstpractical data transfer throughput is higher than the second practicaldata transfer throughput.
 20. The method as claimed in claim 19, furthercomprising: recording an identifier corresponding to the second cell ina black list stored in the memory device when the recorded firstpractical data transfer throughput is higher than the second practicaldata transfer throughput.
 21. The method as claimed in claim 14, furthercomprising: checking whether an identifier corresponding to the secondcell is in a black list; and performing the data transfer in the secondwireless network via the second subscriber identity card when theidentifier corresponding to the second cell is not in the black list.